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Cell biology (Stem cells (Stem cells- undifferentiated cell-- divide to…
Cell biology
Stem cells
Stem cells- undifferentiated cell-- divide to produce more undifferentiated cells. Found in early human embryos- potential to change to any cells, tissue, organ.
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Can be grown in labs to produce clones - made to differentiate into specialised cells for medicine and research.
Can cure diseases e.g. bone marrow- replace faulty blood cells.
Embryonic stem cells- replace faulty cells- make insulin producing cells for the diabetic, nerve cells for paralysed with spinal injuries.
Therapeutic cloning- embryo can be made to have same DNA as patient-same genes; not rejected.
However there is risks- stem cells grown in lab can be contaminated with virus; passed onto patient.
- For:
- Curing existing patients who are suffering- more important than embryo rights.
- Embryos used in research unwanted from fertility clinics--otherwise destroyed.
- Allowed in UK- must follow strict guidelines.
- Against:
- Destroys potential life.
- Scientists- concentrate more on finding and developing other sources of stem cells- not destroying life.
- Some countries ban stem cell research.
- Stem cells produce identical plans:
- In plants- meristems (where growth occurs)- throughout plants life- can differentiate in meristem tissues.
- Can be used to grow rare species- prevent extinction.
- Can be used to grow crops of identical plants that have desired features e.g. disease resistance.
Cells
All living things made of cells.
Eukaryotic- complex (animal and plant cell).............Prokaryotic- small and simple; single-celled (bacteria).
Different parts of cell sub-cellular :arrow_right: structures.
Animal cell:
Nucleus- contains genetic material- controls cell activity.
Cytoplasm- gel-like substance, contains enzymes for chemical reactions.
Cell membrane- holds cell together, controls what goes in and out.
Mitochondria- most aerobic respiration occurs; transfer energy to cell.
Ribosomes- protein synthesis.
Plant cell: (everything with animal cell and more)
Rigid cell wall- made of cellulose, supports cell and strengthens it.
Permanent vacuole- cell sap, weak solution of sugar and salts.
Chloroplasts- Photosynthesis occurs. Contains chlorophyll- absorbs light for photosynthesis.
Bacterial cell:
Don't have nucleus- singular, circular strand of DNA- floats in cytoplasm.
Rings of plasmid DNA. Can also have a flagellum- locomotion.
Chromosomes and mitosis
Cells divide in order to survive and grow. Most cells in body have nucleus- contain genetic material in form of chromosomes.
Chromosomes- coiled up DNA molecules, contain a large number of genes which control development of different characteristics.
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Body cells have 2 copies of each chromosome- mother and father. 23 pairs.
Body cells in multi-cellular organisms divide to produce new cells- cell cycle, division of mitosis--used to grow or replace damaged cells.Cycle results in 2 new identical cells to original cells- same number of chromosomes.
Growth and DNA replication:
1) DNA spread out in long strings.
2) Cell grows and increases in sub-cellular structures- ribosomes and mitochondria.
3) DNA duplicated for each new cell, DNA copied and forms x-shaped chromosomes.
Mitosis:
4) Chromosomes line up at centre of cell and cell fibres pulled apart- 2 arms go at opposite end of cells.
5) Membranes form around each set of chromosomes- become nuclei of 2 new cells- nucleus divided.
6) Cytoplasm and cell membrane divide- 2 new daughter cells produced identical to parent cell.
Cytokinesis- 1 cell becomes 2.
Diffusion
Spreading of particles from area of high to lower concentration- even spread of particles.
Happens in solutions and gases- free to move around.
The bigger the concentration gradient, the faster the diffusion rate. the higher the temperature, faster rate as particles have more energy so move around faster.
Cell membranes- hold cell together and let stuff in and out Dissolved substances move in and out of cells by diffusion. Small molecules diffuse through cells membranes- O2, glucose, amino acids, H2O. Big molecules can't fit through membranes- starch and protein.
Particles flow through membranes from higher to lower concentration- move about randomly so go both ways- but if more particles on one side, that is net movement. Large the surface area of membrane, faster the diffusion rate- more pass through at once.
Osmosis
Movement of H2O molecules across partially permeable membrane from region of higher to lower water concentration.
Partially permeable membrane- contains small holes for tiny molecules e.g. water to pass through.
During osmosis, water molecules pass both ways through membrane- as move about randomly. Because there is more water molecules on one side- steady net flow of water into region with fewer water molecules i.e the stronger sugar solution.
The strong sugar solution gets more dilute- water tries to even up concentration on either side of membrane.
Microscopy
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Light microscope: light and lenses- form unique image if specimen and magnifies. Individual cells and large sub-cellular structures seen e.g. nuclei.
Electron microscope: electrons- higher magnification and resolution than light microscopes- sharper and more detail in smaller things e.g. internal structure of mitochondria.
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